Aqueous microdroplets enable abiotic synthesis and chain extension of unique peptide isomers from free amino acids

Abstract

Amide bond formation, the essential condensation reaction underlying peptide synthesis, is hindered in aqueous systems by the thermodynamic constraints associated with dehydration. This represents a key difficulty for the widely held view that prebiotic chemical evolution leading to the formation of the first biomolecules occurred in an oceanic environment. Recent evidence for the acceleration of chemical reactions at droplet interfaces led us to explore aqueous amino acid droplet chemistry. We report the formation of dipeptide isomer ions from free glycine or L-alanine at the air–water interface of aqueous microdroplets emanating from a single spray source (with or without applied potential) during their flight toward the inlet of a mass spectrometer. The proposed isomeric dipeptide ion is an oxazolidinone that takes fully covalent and ion-neutral complex forms. This structure is consistent with observed fragmentation patterns and its conversion to authentic dipeptide ions upon gentle collisions and for its formation from authentic dipeptides at ultra-low concentrations. It also rationalizes the results of droplet fusion experiments that show that the dipeptide isomer facilitates additional amide bond formation events, yielding authentic tri- through hexapeptides. We propose that the interface of aqueous microdroplets serves as a drying surface that shifts the equilibrium between free amino acids in favor of dehydration via stabilization of the dipeptide isomers. These findings offer a possible solution to the water paradox of biopolymer synthesis in prebiotic chemistry.

Interfacial solute flux promotes emulsification at the water|oil interface

“…The ability to tune the extent of emulsification with the choice of electrolyte provides a robust alternative to spontaneous emulsification methods via more complex strategies. Finally, our results offer insight into a new physical means by which nature can spontaneously produce microcompartments, a topic of intense interest in understanding the abiotic origins of life 27,[30][31][32] .…”

Efficient Desorption and Capture of Reactive Carbocations from Positively Charged Glass Surface Bombarded with High-Speed Water Microdroplets

“…This result suggests the survival of a significant fraction of the reactive carbocation in the DESI secondary microdroplets, despite a small fraction of the carbocation annihilation by the nucleophilic attack of water (H 2 O 18 ). This result is in line with the proposal that carbocations primarily span life at or near the air/water interface, which is effectively water-poor. − …”

Optical trapping and light scattering in atmospheric aerosol science

“…This is a very active area research as the enhancement of chemical reactions in aerosol particles contains many unknowns 319 and is believed to play an important role in prebiotic chemistry. [320][321][322] The study of chemical transformations using Raman scattering from optically trapped particles is limited to systems that contain only a few components; beyond this, the spectra become difficult to analyze. As discussed earlier, this is another area where EDBs have shown promise, as it has been demonstrated that they can be coupled with high performance mass spectrometry.…”